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Vol. 18 (2015 year), No. 1
Kuchina Yu. A., Dolgopyatova N. V., Novikov V. Yu., Konovalova I. N., Prinsteva M. Yu., Sagaidachny V. A.
Thermal decomposition of natural polysaccharides:
Chitin and chitosan
The results of the thermal analysis of shrimp’s chitin and chitosan have been presented (samples of polysaccharide differed by the deacetylation degree have been studied). The thermal analysis has been carried out by differential thermogravimetry and differential scanning calorimetry. Activation energy of process of chitin and chitosan thermal destruction has been calculated
(in Russian, стр.6, fig. 5, tables. 1, ref 6, Adobe PDF, Adobe PDF 0 Kb)
Vol. 19 (2016 year), No. 3, DOI: 10.21443/1560-9278-2016-3
Novikov V. Yu., Dolgopyatova N. V., Konovalova I. N., Kuchina Yu. A.
Properties of aqueous dispersion of chitosan and chondroitin sulfate complex derived from aquatic organisms
Investigation of production of chondroitin sulfate, chitosan and polyelectrolyte complexes based on them received from the local marine raw materials is relevant from the point of view of developing a comprehensive waste-free technology for natural raw materials processing. The objects of study are chitosan derived from the shell of the Kamchatka crab Paralithodes camtschaticus and chondroitin sulfate derived from cartilage of salmon Salmon salar. To determine the surface tension of polyelectrolyte complex solutions and dispersions the Wilhelmy method has been used, the effective radius of particle dispersion has been calculated by light scattering, measurements of effective viscosity have been carried out under shear deformation. The conditions of formation, surface and rheological properties of the chitosan and chondroitin sulfate complex extracted from aquatic organisms in the Barents Sea have been studied. Obtaining conditions and molar ratios of these polyelectrolytes in which the aqueous dispersion of the complex remains stable for a long time have been established. It has been found that by addition of chondroitin sulfate solution to chitosan solution in molar ratios of 1 : 3; 1 : 6 the dispersion of the polyelectrolyte complex stable for 2 to 3 days has been formed. The polyelectrolyte complex dispersions behave as non-Newtonian pseudoplastic liquid. When the molar ratio of the mixed solution is 1 : 1 (regardless of the sequence of mixing) suspension of the polyelectrolyte complex has been formed, then there is precipitation. Equilibrium surface tension of the aqueous dispersion of the polyelectrolyte complex is higher than that of solutions of chondroitin sulfate and chitosan. The effective radius of particles in the complex dispersion has been determined. The effective radius of the particles in the complex dispersion depends on the molar ratio of chondroitin sulfate : chitosan. A qualitative scheme of formation of polyelectrolyte complex from chitosan and chondroitin sulfate as an insoluble precipitate and as a form of stable aqueous dispersion has been proposed. Aqueous dispersions based on chitosan and chondroitin sulfate complex can be used to stabilize suspensions, emulsions, to create foods with a therapeutic and prophylactic properties
(in Russian, стр.8, fig. 4, tables. 1, ref 13, Adobe PDF, Adobe PDF 0 Kb)
Vol. 20 (2017 year), No. 3, DOI: 10.21443/1560-9278-2017-20-3
Novikov V. Yu., Konovalova I. N., Kuchina Yu. A., Dolgopyatova N. V., Cherkun Yu. A.
Hydration mechanism of heterogeneous alkaline deacetylation of chitin
In the work the hypothesis has been proposed explaining the features of the kinetics of chitin/chitosan alkali deacetylation reaction in highly concentrated solutions of sodium hydroxide, which almost completely stops after 30–60 min after the start of the reaction and does not provide a fully deacetylated product – chitosan. Analysis of the known publications explaining the observed decline in the deacetylation reaction rate has been executed, and some new experimental results confirming the authors' conclusions have been presented. It has been shown that water present in the reaction mixture renders the greatest influence on the kinetics of chitin deacetylation, and can lead to hydration as chitin molecules and ions alkalis as well. The hypothesis has been offered according to which in the reaction mixture there is the dynamic balance between hydrated alkali ions, molecules of chitin and formed acetate ion, which can shift depending on the concentration of the reacting particles. It has been suggested that in concentrated alkali solutions water is present almost entirely or partly in the form of hydrate shells of alkali ions, and to a lesser extent in the form of "free" water. Apparently, the limiting stage of the deacetylation reaction is the hydration of chitin macromolecules by water molecules, which are released during nucleophile replacing hydroxyl ions by acetyl radicals binding with chitin amino groups. Acetate ion is a product of the deacetylation reaction. Acetate ion hydration energy is less than hydration energy of hydroxyl ion, so the acetate ion is less hydrated, as a result some water is released. In these conditions, hydration of chitin macromolecules occurs in the local area around the chitin molecules, where the high water concentration is created after deacetylation. The alkali concentration in all reaction volume remains practically constant
(in English, стр.10, fig. 5, tables. 1, ref 31, Adobe PDF, Adobe PDF 0 Kb)
Vol. 24 (2021 year), No. 3, DOI: 10.21443/1560-9278-2021-24-3
Kuchina Y. A., Konovalova I. N. , Novikov V. Y., Dolgopyatova N. V., Kuznetsov V. Y.
Chemical and enzymatic destruction of chondroitin sulfate from Arctic skate
Due to its biocompatibility with human and animal tissues, low toxicity, and biodegradability, chondroitin sulfate (CS) is of great interest for medicine. Since CS is used as a pharmaceutical preparation, its molecular weight and solubility determine the possibilities of its use. This work presents the results of studying the chemical and enzymatic destruction of CS macromolecules and its effect on the molecular weight, solubility and crystallinity degree of the polysaccharide. CS was obtained from the cartilaginous tissue of the Arctic skate (Amblyraja hyperborea). At the stage of cartilage tissue fermentolysis, the enzymes pancreatin, hepatopancreatin and protosubtil were used. The obtained CS samples were identified by IR spectroscopy. Enzymatic destruction of glycosidic bonds in cholesterol macromolecules was carried out with a 1 % solution of the enzyme hepatopancreatin, chemical destruction with hydrogen peroxide and hydrochloric acid. The CS content in the samples was determined by the Dische method. The chemical composition of CS samples was evaluated by standard methods. The average molecular weight (MW) was determined using high performance liquid chromatography and the nephelometric method. The crystallinity degree (CD) was determined by graphical processing of diffraction patterns obtained by X-ray phase analysis of CS samples. It was found that under the action of hepatopancreatin and hydrogen peroxide, deep destruction of chondroitin sulfate occurs, to the formation of low molecular weight and oligomeric fragments. Under conditions of acid destruction in 0.5 N HCl for 20 min the MW of chondroitin sulfate is reduced by 10 % compared to the initial one. Acid destruction causes a significant decrease in the CD of the CS samples. For CS samples not degraded in acid, the solubility in distilled water increases with decreasing MW and CD. The solubility of CS after acid destruction in the range of pH = 5–9 units is 99.0 ± 0.5 %. This high solubility is most likely explained by the significant content of the amorphous phase in the samples.
(in Russian, стр.9, fig. 5, tables. 2, ref 24, AdobePDF, AdobePDF 0 Kb)